Experimental study of current density in copper filling process within deep through-silicon vias with high aspect ratio

Abstract

Current density is one of the process parameters with the most significant effect on through-silicon via (TSV) filling. However, the mechanism analysis of the influence of current density on TSV filling morphology lacks experimental demonstration. In this work, electrochemical deposition experiments and electrochemical analysis experiments were carried out to investigate the effect of current density on the copper filling within deep TSV with high aspect ratio. Three typical filling morphologies and corresponding evolution of the plating were observed. Additionally, the influence of current density on the competitive adsorption relationship between accelerator and suppressor was discussed based on the electrochemical measurement results. Furthermore, the diffusion time of additives was measured. The indirect effect of the current density on the local concentration of additives was discussed. Finally, three filling patterns were proposed to explain the effect current density on the filling process of deep TSV with high aspect ratio.